Violent releases from methane clathrates are one of the suspected causes of the Paleoecene-Eocene Thermal Maximum (PETM), which led to an increase in global tem

Violent releases from methane clathrates are one of the suspected causes of the Paleoecene-Eocene Thermal Maximum (PETM), which led to an increase in global temperatures in excess of 5 degrees C. The PETM was not really associated with any mass extinction events on land (to the contrary, it drove rapid specification in mammals). But the oceans are a different story. The ocean is generally extremely stable, so ocean life generally does not respond well to rapid environmental changes.